For the nth time, I missed this step in a new deployment, so blogging it down to remember for prosperity. Of course I will have to not forget to remember to this post.

Problem:

Control Adapters are not loaded in a SharePoint site.

Pre-checks:

If the control adapter is part of a solution, ensure that the solution is deployed correctly (Get-SPSolution and the Deployed column is set to True)
Check the .browser file is uploaded correctly in all the WFE’s (App_Browsers directory)